Field of the Invention
The present invention relates to an apparatus for preventing a fuel within a fuel tank of a vehicle from flowing out of the fuel tank via a passage connected to a canister at the time of a vehicle's being in a severe turning position or a sharply-steep road.
Description of the Prior Art
A vehicle is provided with a canister for absorbing a fuel vapor produced by evaporating the fuel within a fuel tank by a change of a temperature and for transmitting the fuel vapor to the inlet system of an engine together with purge air flowed by a negative pressure produced at the time of driving of an engine.
Such a fuel vapor re-circulation system is installed in all kinds of automotive vehicles to restrain discharge gas, and this canister communicates with the fuel tank installed in a vehicle via a vent tube.
If the fuel in the fuel tank is evaporated by a temperature change, a gas generated by the evaporated fuel moves to the canister. In such a structure, the fuel inside the fuel tank flows back to the canister via the fuel vapor vent tube at the time of the vehicle's being in a severe turning position or sharply-steep road, or rolling over.
As a method for solving this problem, a check valve means is installed between the fuel tank and the canister so that the fuel does not flow backwards.
If this means is disposed between vent tubes, in a case that the vent tubes are broken, the fuel within the fuel tank may flow out to the atmospheric air. Thus, it is preferable that the check valve means is disposed within the fuel tank.
Japanese Patent Unexamined Publication No. 92-151332 discloses a method for preventing the outflow of a fuel in any case by controlling pressure within a fuel tank, simultaneously with preventing escape of the fuel from within this fuel tank.
According to this method, there are provided a guide wall for guiding the lift of a float that is provided on a wall under a case, and a stopper limiting the rise of the float on the guide wall to prevent the outflow of the fuel by the rise of the float. If the pressure within the fuel tank increases, the stopper controls the rise of the float.
In such a system, the stopper suppresses the rise of the float, and it depends on the height of a casing, the thickness of an upper substrate and their quality of material in order that the stopper drops the float at a position the float ascends maximum. Thus, when the fuel tank is in the state of high pressure, effects as desired cannot be attained.